How to Install & Dual Boot Mac OS X 10.7 Lion and 10.6 Snow Leopard

Mac OS X 10.7 Developer Preview can be installed and ran alongside Mac OS X 10.6 on the same drive, all you need to do is partition your existing boot disk and I’m going to show you exactly how to do this in a step-by-step guide (alternatively, you can run it in VMware too).

Why do this? Having two separate installations of Mac OS X has several advantages over installing Lion atop your existing 10.6 installation (the default method), here are the primary reasons I recommend dual booting instead:

Installing future 10.7 Lion releases will be easier

You are free to uninstall Lion at any time – without dual booting this requires a system restore from a 10.6 backup

You don’t have to use Lion as your primary operating system – remember it’s a developer preview and not intended for every day use

Now I’m going to assume you already have Mac OS X 10.7 Lion downloaded (grab Developer Preview from Apple) and ready to go, and that you’re currently running Mac OS X 10.6.

Important: Make sure you have a backup of your existing Mac OS X installation and disk before continuing with this guide. Time Machine makes this very easy. Any time you edit a drives partition table or install a new operating system there is always a small chance something could go wrong, so just be safe and have a backup ready.

Let’s get started!

1) Create a partition for Mac OS X Lion

You can create a new partition on your hard drive with Disk Utility, this does not require you to reformat the drive and you should not lose any data (besides, you have that backup just in case something goes wrong, right?).

Launch Disk Utility

Select your hard drive from the left hand side

Click on the “Partition” tab at the top

Click on the “+” icon to add a new partition, name it ‘Lion’, or chimichanga, or whatever you want

Set the partition size for Lion, I chose 20GB to make it easy

Click on ‘Apply’ to create the new partition, and you’ll see a message like this one:

Click on “Partition” to create the partitions as indicated

You’ll now see two partitions on your boot drive in Disk Utility, one that has your existing operating system (Mac OS X 10.6) and the newly created “Lion” partition, which is where you will install Mac OS X 10.7. It will look something like this:

Now that you have the partitions squared away, we’re on to step 2.

2) Install Mac OS X 10.7 Lion on the new partition

Now it’s time to install 10.7. The key here is to install Lion on the newly created partition and not the default which is atop 10.6. This is what will enable you to dual boot between 10.7 and 10.6:

Launch the Mac OS X 10.7 Installer and when it asks what drive to install on, choose the options to specify your own

At the “Install Mac OS X” screen, click to select the partition that you created in Step 1, I named it Lion as you can see in this screenshot:

Just let this be as it runs. You’ll see a preparation window and then your Mac will reboot into the full installer. Due to the fact that you are installing from your local disk to another partition, the whole process is much faster than it would be to install from a DVD. On my MacBook Air 11″ the entire Lion installation took about 15 minutes.

When Lion is finished installing, your Mac will now automatically boot into 10.7.

Now that Lion is installed, your default boot drive is set to 10.7. You can adjust this to be 10.6 too:

Launch System Preferences

Click on “Startup Disks”

Select your default boot drive and operating system

That’s really all there is to it.

4) Dual Booting: Select which Mac OS X volume to load on boot

If you want to boot into a different Mac OS X installation than the one that is set as your default in the previous step, you can hold down the Option key during reboot. You will then see a boot loader like the image at the very top of this tutorial, where you can select which Mac OS X version and volume to boot from.

This is dual booting at it’s finest, and this is the best way to run the Lion Developer Preview. Remember, this is a developer preview for a reason, it’s not meant to be a stable operating system for daily use. Many have installed 10.7 Lion on top of their existing 10.6 Snow Leopard installation, and while this may be the easiest method it can’t be directly undone and instead requires a complete system restoration to uninstall and revert back to Snow Leopard. That’s a huge pain, just give Lion it’s own partition and make it easy on yourself.

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Jowan, I know I’m late to this thread, but if you’re still around, I’m wondering how you accomplished this.

I installed windows 7 using bootcamp, worked fine. Then I used Disk Utility to split off a small part of Partition #1, to install Snow Leopard on — and now I can’t boot into Windows anymore!

* Disk Utility, the Finder and the Startup Disk preference pane all still show the Boot Camp volume, with all the files intact.

* When I boot holding down the option key, all I see are 10.7 and the restore partition.

* When I select “BOOTCAMP – Windows) in the Startup pane and restart, the computer holds for several minutes on a blank gray screen. Then I get a black screen with white DOS-like text that says “No bootable disk — insert boot disk and press any key.”

If I am not mistaken, Bootcamp requires it to be in the last partition but with a maximum of 3 partitions. If you go beyond 3 partitions, Windows will not be able to boot. With Lion, the problem is that the new Recovery Hd takes up a partition. Therefore, it is not possible for Windows to boot. Instead, you will have to remove that recovery partition, or just have Lion, Lion Recovery and Bootcamp.

I know this is a late comment, but you have two choices.
1. Partition your disk and install Snow Leopard and then get Lion and partition your disk again to triple boot.
2. Install Lion in an emulator like VMWare Fusion or Parallels Desktop (recommend VMWare more)

“Many have installed 10.7 Lion on top of their existing 10.6 Snow Leopard installation, and while this may be the easiest method it can’t be directly undone and instead requires a complete system restoration to uninstall and revert back to Snow Leopard. That’s a huge pain, just give Lion it’s own partition and make it easy on yourself.”

This is the problem I have. Installed Lion on top of Snow Leopard and now have to revert to SL as Dropbox (essential for me) won’t run under Lion.

Have you tried restoring from a time-machine backup? If you have that option, plug in your time machine external drive and hold the option key. Choose the time machine recovery drive and it should restore your system.

I could be wrong, though. I would also recommend trying a fresh install of 10.6 as it was an ‘archive and install’ and shouldn’t erase your files.

I tried this to restore my system onto a blank drive after replacing my old one for a larger size, and the time machine restore didn’t install the OS on the new drive, i couldnt boot form the thing anyway. As far as I could tell, it had installed all the stuff from my backup, but just not a bootable copy of the OS, so I had to re-install SL while booting from my disc. I think you could do the same to overwrite Lion with a copy os SL from the SL install discs, without damaging the files on the disc? Not sure if thats how it works or not though

[…] to run it yourself? Check out our guide to install Mac OS X 10.7 on a separate partition and dual boot with 10.6, it’s the best way to try out Lion without messing with your stable Snow Leopard […]

[…] you skipped the first Developer Preview release and you want to try Developer Preview 2, you can dual boot and install Lion alongside 10.6 without formatting your drive. Note that you’ll want the standalone download if you choose […]

Not at all, you can just delete the partition through Disk Utility. That said, you should always have a recent backup of your Mac before you change the partition scheme just in case something goes wrong.

I have the same problem after installing Lion osx full release made a small partition everything seems fine bu wanted to now resize and it will not let me? So tried to add a new partition and install again and it says need a newer version of osx to do so? I have the latest SL. Then tried to delete the Lion partition and start from scratch and it says again newer version of OSx needed? stuck any help? Thanks

No – but just boot up from it – don’t charge ahead with any of the Install process! – but look up in the menu and choose Disk Utility.

You also may also do this to run repairs on boot disk if needed or to check if a startup problem is software or hardware (If it boots from installer but not from normal system then it indicates a problem with system and not with hardware)

Hi,
I’m having problems installing Lion Preview 2. I have Lion 1 installed on a partition drive and I did the update from software update. I get all the way through and went it asks me to hit the restart…I get this message

An error occurred while preparing the installation. Try running it application again. If the problem persist, use Startup Disk to restart your computer from the Mac OS X install DVD.

I’ve re-did this at least 6 times and I keep getting the same message. I installed Lion 1 with no problems. Can someone please try and help me out to figure out, on why this won’t install?

[…] the data from, I don’t know. Now you might say my situation is unique because My MacBook Air dual boots between Lion and Snow Leopard, but upon looking at some friends Macs I discovered that even in a single boot setup, a startup […]

[…] especially important when using a beta OS, which is also why I’ll continue recommending the dual boot method if you plan on trying out the Lion preview releases. For those who aren’t developers, Mac OS […]

I am new to mac, and this might sound silly, but I was wondering…I installed mac os x lion aside mac os snow leopard (dual boot). I noticed when using mac os x lion, the system uses software which is installed on snow leopard but not on lion itself. How is that possible? An example – I wanted to open a .rar file. I have a software installed for this on snow leopard, but not on os lion. But os lion managed to open .rar file using the software which is installed on snow leopard.

Thanks for quick instructions..I got my Preview last night and almost had unstoppable inclined to install on Leopard..but didnt do it..Glad to see this in the morning now again i can resist to go home and get my hand on Lion ;)

[…] this is the same requirement for past clean Mac OS X installs. I did precisely this in my post explaining how to dual boot Mac OS X Lion and Snow Leopard. I won’t walk through that entire post again, but I can tell you with 100% certainty that I […]

Yes, you could delete Snow Leopard but I would not recommend doing that until the final version of Mac OS X Lion is released next month. The final release of Lion will be downloadable from the Mac App Store via Snow Leopard, and you will probably want to perform a clean install of it rather than upgrade over the developer betas.

Great tuorial, thanks. For the GM version, it seems we have to copy the installation file to the partition where Lion is installed to get it running, otherwise the reboot step doesn’t work (auto reboot to Mac Snow)

If I have Lion installed on a separate partition and later want to delete my old Snow Leopard partition, how I can get all my third-party software (Adobe CS5, Office 2011, Parallels, etc.) to the new partition? What about old emails, photos, iTunes music etc? Or, is all that done automatically during the Lion install. Thanks in advance.

Installing Lion on a separate partition creates a clean install that does not include any of your old apps, emails, or photos. If you want to have all of your old apps and documents, you can either restore from a Time Machine backup or better yet just upgrade from Mac OS X Snow Leopard to Lion directly.

I created a new partition and flashed the Lion image to it and ran the install from there. Now I have my old Snow Leopard install, Lion, the Lion disk image and a hidden “Recovery HD” partition. I know that Recovery HD IS basically the bootable disk, but how do I delete the partition I flashed the image to?

It’s acting as if it’s also Recovery HD, which I know you can’t delete. Obviously I don’t need 2 install disks but I can’t seem to delete the one I created.

I wasted my half of the day in the same issue saying “an error occured while preparing the installation .Try running this application again”

but I found a way to solve this issue , it worked for me you should try this out.

1. open disk utility–> mount lion.dmg–>create two partitions one of 20 Gb where you will actually install Lion OS other 10 GB for temporary use.

2. In disk utility use restore option source will be your Lion installation media in my case it was lion.dmg file,, destination will be 10 GB temp partition which we created above, now restore it , wait for 8-10 minutes.

3. Once this is restored in 10 GB temp partition, open temp partition and run installation from there instead of Lion.dmg what you were doing earlier.

4. It worked for me , while writing here second Lion installation is going on on 3 of My mac pro servers.

[…] you are completely dependent on one of these PPC apps, you may want to try a dual boot OS X 10.6 and 10.7 configuration, or just skip upgrading to Lion until a Lion-compatible version of that app is made […]

Hello,
i created a partition to try Lion,
Now i erased that partition so that i can create a partition with more GB of space, but the system doesnºt let me eliminate the lion partition, saying it needs a newer system to allow elimination o f that partiotion.

I still have snow leopard in main partitiont.
Can anyone tell me how to erase lion partition i have created, though snow leopard?

SWEET tutorial. Couldn’t be more to the point and clear than this. One question though, in case I get tired of dual booting and decide to keep Lion as my main OS how can I delete the Snow Leopard partition to merge it with the Lion partition BUT still keep all my files and applications from SL in Lion.

I think many people will decide to do this at one point and a tutorial would be GREAT. Thank You

I’ve installed Lion on a partition dual boot as above. Can I access all the applications on Snow Leopard from Lion or do I have to re-install them all, given that the partition is only 40GB that may be problematic?

This may be a stupid question – related to security/access. When i Boot Lion, I “see” the SnowL partition as another internal drive. I can access parts of it, but, when trying to get at my old “stuff” (like the pictures directory), finder shows it with a “universal wrong way” sign (Red circle, with white line) – basically, no permissions. I can use my Lion permissions to change the permissions, but, what can I do in setting up Lion to use the same Administrative account, or, whatever? Thanks.

I am in a similar situation to David as I cannot function without some of my PowerPC applications (Quicken 2007 for Mac, etc, etc). As I have already transitioned to Lion, can I create a new partition, reinstall Snow Leopard and have access to the tools that I am desperately missing? Any special considerations going at this backwards? Thanks for your assistance. Am desperate. BIG lesson learned. Will look before I jump next time!!!

Thanks. I have a similar problem but in reverse. I have a Macbook Air 2011. Came with Lion and now want to install 10.6. Won’t boot from install disk in remote computer or from a bootable USB drive with 10.6 installed. Is there any way to get 10.6 to install if 10.7 is the default? Can you install with Fusion?

What is the message you get when trying to resize the Lion partition? It should let you increase the size of it all the way, be sure you have a backup ready but you could also try booting from the Recovery partition.

Is that 100gb of freespace at the beginning of the drive? I suspect it is. I would like to know if there is a way to move the Lion partition back to the beginning of the drive so it could use that space.

0) Using Disk Utility.
1) Add a partition into the “Free space” your created previously.
2) Restore your Lion partition to the first partition.
3) Restart holding donw the OPTION key….
4) Select the New Lion partition as your boot partition
5) Delete the Old Lion partition with Disk Utility
6) Drag the New partition to be full size if that is what you want.
7) Apply

HELP!! I installed lion onto my main drive (just discovered this partitioning business after much research) and desperately want to revert back to leopard. I do not like lion, it will not let me into my security settings for starters and having fraudulant activity from
My visa! I do not have a time capsule and my computer comes up with error when trying to create a partition. Everything is on my computer… Programmes like ps5 and microsoft word and I nearly re installed sniw leopard until my gut feeling told me I was about to completely restore it from moment I purchased my imac. Please someone help me :(

I could use some Help. Ok Recently purchased an iMac i7 that was running Snow Leopard.

I am a musician that runs a special set up in Logic with plugins that I’ve been collecting over the years. So with that being said I usually boot from an external drive with my (Monster Logic Set up Installed).

So I decided to install Lion on the iMacs internal drive over Snow Leopard. Everything went ok with the that, but now when trying to boot from my external HD (with the Monster Logic Set Up Installed) it wont boot. The the icons will show up for the Hard Drives that I can boot from but once selected. Nothing the apple logo comes up but no pinwheel or anything. I then will have to do a hard reset to boot back to the internal drive.

I hope that some one can help me with this. I’ve been booting with this same external drive for almost 3 years now.

Good day sir.. i am currently running mac os x lion 10.7.1, is it possible to bootcamp mac os x snow leopard? i am having problems with some of the drivers i use for my Djing stuff with the lion because numark haven’t published new drivers yet for the lion.. is it possible to bootcamp os x snow leopard from my os x lion sir? hoping to hear from you soon.. thanks..

We’ve just found a way to install Snow Leopard within Lion, using Parallels. So you don’t have to choose which one you want to boot into; you can run both simultaneously. There are two methods, actually, both are on our blog. We hope these instructions are useful to others.

how do i install windows 7? ive done the partition step and i put the windows intallation disc and blah blah clicked ‘upgrade’ but when it said ‘ eject disc and restart so the windows starts normally’ i cant eject the disc and so i pressed the power button and restart it clicked the eject button and trackpad the disk came out but it didnt start with windows. im so confused please answer my question.

Problem is – I tried to boot from a external HD running Snow Leopard on my new Mac which runs Lion. After selecting the HD all I get is the Apple start up screen and 3beeps (on repeat).
The only reason I’m doing this is because some of my software isn’t even supported by Lion!
Any help on how to boot SL over Lion from an external would be much appreciated.
Thanks in advance

In August, 2011 I bought a Mac Pro that came with Lion. I want to install Snow Leopard on an external disk. I bought the SL CD v. 10.6.3 and tried installing but I get an error when trying to use the SN installer. I can’t boot from the CD either. Apple Support had no answer. Please help.

Hi!
Question: I have Lion (OS X 10.7) installed on top of 10.6. but now I want to go back to 10.6 without deinstalling Lion again.
I already made a second partition, but when I want to install 10.6 from my DVD I get an error message: “you cannot use this program on this version of mac os x”. What can I do?

I am considering a purchase of a MacBook Air 13 inch, that comes with Lion 10.7 OS. I have a 15 inch MacBook Pro with 12 years of Quicken 2006 for the Mac data on it running 10.6 Leopard. Will I be able to partition off part of the MacBook Air hard drive & install 10.6 Leopard & install the Quicken App to run my data & continue to use it. This may be especially challenging without an optical disc drive on the MacBook Air. Would Parallels be an easier fix?
Thanks
Steve

I installed Lion from a DMG. My final Cut pro seemed to work fine for a day or so then wouldn’t open up. So installed Snow Leopard from my old install disc on my 2nd internal drive. It seemed to install OK but my final cut pro 7 doesn’t work still. What do you suggest?

I’ve bought a new IMac with 10.7.2. I have old PPC programs. I partitioned the HD and tried to install Leopard but the Mac refused. Apple says I cannot install older version on this hardware. Any ideas?? I’ve tried Parallels with no better success.

Will this work to install 10.5 (instead of 10.7) on my 10.6.8 machine? I have an application (Quickbooks Mac 2007) that stopped working properly on 10.6.8 because the company is no longer supporting that application. Please respond on site and with email.

Ok so here it goes. I have a 13” Early 2011 MBP 8,1 (native Snow Leopard, now running Mavericks) and a 15” Late 2011 MBP 8,2 (native Lion sans install/recovery media/usb drive). The 13” is working perfectly. The 15” is at the moment being forced to run a very dodgy linux distro/self-built mod pack because I screwed up somewhere. I had it dual booting Windows 7 and OS X Mavericks using Bootcamp. (Don’t ask me why, ok? I am not enjoying my gigantic helping of disgusting MS Windows crow.) When i came to my senses and decided to kick Windows finally, I decided on a clean install so therefore set off to copy off the wanted files before heading over to boot and use disk utility. Well it seems i screwed up, and I’m assuming its due to some weird bootcamp step i simply ignored. Well the point is now i cannot get it to boot at all. I’m stuck with an EFI Password I never set now. No SU mode, No Target Disk Mode, No Recovery Mode, I can’t get into it at all unless i use a Linux liveDVD and install. Is there a way i can fix the bootloader so i can load a recovery HD and remove the EFI Password, and finally use it again like normal??? HELP!!!!!